-Reuters - Khaled Yacoub Oweis

Rivalry between Qatar and Saudi Arabia has fuelled wrangling within the Syrian opposition that threatens to prevent a united opposition delegation attending international peace talks next week.

Sources in the opposition coalition and diplomats from foreign powers backing the opposition said it remains unclear whether those divisions can be overcome by Friday, when the 120-member Coalition is expected to vote on whether to take part in the conference in Switzerland known as Geneva-2.

However, some expect that Qatar, which raised its profile in diplomacy by being quick to back the Arab Spring revolts, will not in the end risk angering Riyadh, Turkey and Western states by having Doha's allies on the Coalition force a boycott of talks that are supported by the other powers.

Earlier this month, 44 members, mostly with links to Qatar, walked out of a Coalition meeting to underline their rejection of attending talks without assurances that key demands would be met. They were also angered by the re-election of Ahmad al-Jarba, a Saudi-backed Syrian tribal figure, as head of the Coalition.

Diplomats said Qatar's role, which includes supporting some militant Islamist brigades in Syria, had been discussed at a meeting in Paris on Sunday of the so called "Friends of Syria", a group supporting the opposition, which was attended by U.S Secretary of State "John Kerry" and other Western foreign ministers.

"The message was that everyone needed to be on a new page in support of Geneva and stop backing militants", a person who was at the meeting said. "There were strong hints that the onus falls on Qatar for a Coalition decision to go to the talks".

Qatar's foreign minister insisted in Paris that the Gulf emirate was not backing one opposition faction over another.

Few members of the Coalition are enthusiastic about the meeting, organised by international powers anxious to end the conflict which has destabilised the Middle East for three years.

Coalition members see little prospect of Syrian opposition delegates making big concessions, let along agreeing to their demand of a transitional administration that excludes president al-Assad from power. As a result, they fear attendance could further undermine their legitimacy within a Syrian opposition that is increasingly dominated by jihadist fighters on the ground.

However, a failure to show up next Wednesday would dismay most of the opposition's foreign backers. They might scale back their support for a body that has failed to prevent much of the rebel force in Syria becoming dominated by Islamist militants.

"The Coalition is being asked to go to Geneva without a hint that the talks will result in anything even to save face before the Syrian people", said Nasr al-Hariri, spokesman for the 44 members who walked out this month. "The only way for the Coalition to function as a coalition is by expanding it to restore balance and find a consensus president".

Even those close to Saudi-backed Coalition chief al-Jarba say they are reluctant to go to Switzerland without some assurance of winning concessions, such as the release of prisoners or the lifting of sieges around opposition-held suburbs of Damascus.

Though allies in other respects, the Gulf monarchies of Qatar and Saudi Arabia have ended up backing rival forces in some Arab states where power has changed hands since 2011. For example, Qatar backed Egypt's Muslim Brotherhood, Saudi Arabia the military who toppled the Islamist president last year.

In Syria, with the country at the heart of the region fragmenting into competing spheres of influence, Qatar carved an influential role by being quick to help the militant and, later, by helping set up the Coalition a year ago .

Last year, however, Qatar found itself under pressure from its much larger neighbour and from the U.S superpower over the way the war was going, and notably over the rising influence on the frontlines of Islamists hostile to the West and to its allies in the Middle East - like the Saudi royal house.

An expansion of the Coalition to 120 seats diluted Qatari control and handed leadership to the Saudi-backed al-Jarba. On the ground, however, Qatar is still a force, through groups like al-Tawhid, part of a new Islamic Front that controls large areas and coordinates with the al Qaeda-linked al-Nusra Front.

"There are military groups in the opposition that are more influenced by Qatar than Saudi Arabia. But within the Coalition Saudi Arabia is stronger," said Abdelrahman al-Haj, a senior official in the opposition council.

A Gulf source with knowledge of Qatari policy said the new emir, in power since June, wanted a lower profile than his father who had strongly backed the Arab revolts. The new emir was also more open to Western requests to stop supporting militants.

Diplomats involved in negotiations with Doha say Qatar still appears lukewarm toward Geneva-2. Some note that its ally in Syria, the Islamic Front, issued a statement supporting those members who had walked out of the Coalition.

Personal differences are also playing a role in the wrangling over whether to attend the meetings at Montreux.

People who know both men said that Mustafa al-Sabbagh, Qatar's point man on the Coalition, and Riad Hijab, who ran against al-Jarba for the presidency, could give their blessing to participation at Geneva-2 - if they and their allies secure a suitable presence in the delegation to the talks.

One senior member of the Syrian opposition familiar with the factional in-fighting said Qatar may not be willing to risk the Saudi and Western backlash that could follow a failure of the Coalition to send a cohesive delegation to the meetings.

" Qatar has carved itself a powerful niche by supporting the Islamic Front and using it as a pressure tool on the coalition", he said. "But at the end of the day Qatar will not defy Saudi Arabia and the United States.

"Its people in the Coalition need its financial and political support and so will do what Qatar asks".

However, Ahmed Kamel, a pro-opposition Syrian political commentator, said "Qatar might fail to persuade allies on the Coalition to negotiate with Assad's team: Part of the crisis is the standoff between Saudi Arabia and Qatar", Kamel said.

"But there is a genuine problem that faces even Jarba - because the Coalition is being asked to go to a peace conference without any conditions, without guarantees and without an agenda".

Western diplomats, however, are pressing hard for the Coalition to attend, stressing the lack of alternatives to the main international initiative to end three years of fighting that has killed over 100,000 people:

One said: "No one wants to think of the alternative if the Coalition fails again to agree".